EP1815632A1

EP1815632A1 - Tool and method for planning and/or dimensioning satellite telecommunications through a quality indicator

Info

Publication number: EP1815632A1
Application number: EP05807995A
Authority: EP
Inventors: Patrick Bruas
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2004-11-10
Filing date: 2005-11-10
Publication date: 2007-08-08
Anticipated expiration: 2025-11-10
Also published as: US7925218B2; EP1815632B1; US20080268788A1; FR2877785A1; FR2877785B1; WO2006051095A1

Abstract

The invention concerns a method for planning and/or dimensioning links between several stations in a wireless telecommunication system including the following steps: a) establishing a relationship, on logarithmic scale, through an existing link between the ground equivalent radiated power, PIREsol, the signal/noise density ratio required (C/No)req for a link, and a quality indicator QaF, b) determining the quality indicator QaF from the contribution of first type stations (of the link budget disturbance) which are linear in PIREsol and of second type stations which are non-linear in PIREsol, c) determining the PIREsol from the quality indicator QaF determined at step b).

Description

TOOL AND METHOD FOR PLANNING AND / OR DIMENSIONING SATELLITE TELECOMMUNICATIONS THROUGH AN INDICATOR

QUALITY

The invention relates to a tool for assisting the planning of satellite telecommunications links. It is also used to size these links.

Satellite communications allow high-speed traffic to flow between any two subscribers in the coverage of the antennal board system via a transparent repeater, provided the link budget allows it.

A link budget calculation algorithm Satcom generally calculates the equivalent isotropic radiated power ground or EIR _SO | necessary for a terrestrial station A, for a given terrestrial station B to receive a signal ratio on total noise density C / No which is required by the link, at a user bit rate D and a bit error rate TEB for a given environment of propagation and interference, via a known payload (space segment) and with a certain margin M system.

A link budget calculation algorithm Satcom generally calculates one of the following quantities:

• the EIR ground in dBW required for a given torque (D, Eb / No), with Eb the average energy received per bit of the user traffic,

• the maximum Flow D for a given pair (EIR ground, Eb / No),

• the Eb / No needed for a given pair (EAR ground, D). The specification of the ground segment modem makes it possible to calculate the ratio average power received on total noise density C / No required by the demodulator. This ratio is given by the following formula (in logarithmic form):

The canonical satellite link budget formula in linear form for a transparent repeater (ie non-regenerative) is:

= (C / Nθ) ^"1 _th uplink + (C / Nθ) ^{" 1} _th dowπhnk

+ other terms (eg interference, intermodulation) [E2]

The left-hand term is calculated from the result of the calculation of each of the perturbation terms {(C / No) ^"1 of index i}, also called stations that intervene in this sum of inverses. = 2 with the terms rising thermal noise (th_uplink) and thermal downward noise (th_downlink).

The condition of success of the link budget is as follows:

According to the methods of the prior art, the calculation of [E2] is carried out on a linear scale after conversion of each of the positions of the logarithmic scale to the linear scale.

Some state-of-the-art calculation algorithms are based on a countdown calculation: we start from a point of C / No received and then go back to the EIRP satellite then to the EIR ground via the operational gain. Then a convergence loop repeats the calculation until the total C / No is equal to the required C / No.

The link budget calculation also serves to size the stations (in power amplifiers and ground antennal system) for a given payload and a given traffic rate. The invention is based on a new approach of tool and device for calculating link budget and / or dimensioning of a link which consists in particular in determining a quality indicator. relevant designated in the following description by QaF. This "total quality figure" is a quality indicator that corresponds to the English acronym QaF meaning "Quality aggregate Figure".

This quality indicator corresponds to a proportionality coefficient, expressed in dBHz / W, between the total signal / total noise density ratio C / No required for the link and the required EIRPW of the carrier of this link. There is therefore an exchange between the PIREsol and the signal ratio on total noise density C / No required (in dBHz). This exchange is expressed by the relation [E4] mentioned below.

The invention relates to a method for planning and / or dimensioning links between several stations or stations, comprising at least the following steps: a) establishing a relationship, by existing link, in logarithmic scale, between the equivalent ground radiated power, PIREsol, the required signal-to-noise density ratio (C / No) req for a link, and a quality indicator QaF, b) determining the quality indicator QaF from the contribution of the first-category items which are linear in PIREsol and posts of the second kind that are non-linear in PIREsol.

The method may comprise a step c) of determining the EIRSol from the QaF quality indicator determined in step b).

The invention also relates to a device for planning and / or dimensioning links between several stations in a telecommunications system, the device being adapted to perform the process steps mentioned above.

The method according to the invention notably provides assistance in the planning and dimensioning of satellite telecommunications links. In particular, it offers the following advantages: • The QaF quality indicator is independent of the modem and EIR ground. • This indicator establishes a relation of exchange especially between the following quantities: the flow D, the ratio Eb / No, the system margin, the receiving antenna surface and the PIREsol for a given payload (characterized by its coverage, its merit factor (G / T) sat, DFS saturation flux density, and repetitive satirical EIRP) and for a given propagation and interference environment. This relationship is useful in Satcom network architecture.

Other features and advantages of the present invention will appear better on reading the description which follows, of an exemplary embodiment given by way of illustration and in no way limiting attached, figures which represent:

• Figure 1 an example of architecture with several stations involved in the Satcom link budget,

FIG. 2 a functional block diagram of the method according to the invention,

FIG. 3 the structure of the elementary "butterfly" operator used in the process;

• Figure 4 the architecture of the calculation algorithm of the PIREsol with terms of the first kind only,

• Figure 5 an example of calculation of EIRP soil with terms of first and second kind,

• Figure 6 the architecture of the "butterfly" operator for cases where there are terms of the first kind and of the second kind, • Figure 7 different curves of quality indicator depending on the antenna surfaces reception and satellite coverage.

In order to better understand the invention, the following description is given in the context of a satcom link. Figure 1 gives an example of point-to-point links that illustrates the presence of seven disturbance stations in the link budget: • Item 1: (C / No) i = Thermal amount

• Station 2: (C / No) ₂ = Thermal downhill

• Item 3: (C / No) ₃ = Scrambling Amount

• Station 4: (C / No) ₄ = Adjacent upstream system interference (example: Skynet Terminal)

• Item 5: (C / No) ₅ = Adjacent downlink system interference

(example: Satellite Skynet)

• Item 6: (C / No) ₆ = Intermodulation ground segment (IM ground)

• Item 7: (C / No) ₇ = Space Segment Intermodulation (IM Edge)

FIG. 2 represents a functional block diagram of the implementation of the method according to the invention.

For example, the planning and assistance tool for link sizing is implemented in a centralized management center 1, the network or CGR (ie the set of communication units (CUs) which are point-to-point link ends. point via the same repeater, each communication unit UC physically belonging to a Satcom station). The centralized management center CGR provides the list of values of the PIREsol, link by link, which will be distributed to each local management center which is attached to a station. Then, knowing the transmission channel gain between the output Fl (intermediate frequency) of the station modem and the antenna output of the station, the local management center will convert the PIREsol F emission power that will be used to configure the corresponding modem at the link. The centralized network management center may optionally provide the operator with graphical and tabulated help by presenting the sensitivity of the quality indicator to the following parameters: receive antenna area, coverage and / or operational gain of the repeater, interference level, station elevation angle, attenuation margins, etc. The centralized management center includes a processor for performing the various steps of the method according to the invention, and the local management centers are also equipped with programmed processors. Satcom planning includes determining the

PERsol of each link and resource consumption for a given deployment.

In summary, the method of assisting the planning of telecommunications by satellite comprises for example the following steps: 1 - determining the contribution of the linear stations in PIREsol,

2 - determine the contribution of potential items that are nonlinear in PIREsol,

3 - determine the QaF quality indicator from the results of 1 and 2,

4 - determine the EIRP, taking into account the results of 3 and the required (C / No).

The quality indicator QaF in practice represents the number of kbps (kilobits per second) of useful information that it is possible to go through Watt of EIR station consumed per link. The quality indicator QaF corresponds to a standardized EIRP by making the ratio in linear scale of C / No (ratio signal to density of total noise) required by the link on the EIRP.

The method includes a step in which logarithmic relationship is established by a link between the EIRPol, the signal to total noise density ratio required by the link, and a QaF quality indicator.

PIREsoi = f - I - QaF [E4]

VNoJ _1C q The stations participating in the liaison report can be of two kinds:

• "p" terms of the first kind that are linear in PIREsol,

• "n-p" terms of the second kind that are not linear in PIREsol.

Considering these two types of positions, the canonical equation [E2] becomes:

To obtain the quality indicator QaF, the process will factorize the EIRPOL in the positions of 1 ^ΘrΘ species as opposed to the 2 ^πdΘ species, in which the EIRP can not be factored. The process considers all the terms of 1 ^ΘrΘ species as a product (in linear scale) of the PIREsol and a paralleling of the contributions of the different items of 1 ^ΘrΘ species.

To determine the quality indicator values, a "butterfly" operator is defined (by analogy with the elementary fast FFT operator). Figure 3 shows an example of structure of this operator.

Butterfly (R ₁ , R ₂ , sign) = min (R ₁ , R ₂ ) -10logi ₀ (1 + sign .1 ₀ ⁽ - ^{| (R1} - ^{R2) / 10 |)} ) [E6] With: sign = ± 1 chosen according to the species of the disturbing stations.

Ri and R ₂ are expressed in dBHz / W and correspond to the two disturbing stations concerned by the grouping, Ri is the individual quality factor of item i, a detailed example is given below in the description. In the figures, the letters A and B represent the inputs of the operator and the letters D and C the output of the throttle operator.

The algorithms implemented in the planning tool depend on the stations involved. For linear positions

Posts are grouped 2 by 2 and the +1 sign is used in the designated operator "butterfly"

FM // R2 = Butterfly (FM, R2. +1) [E7] with a repetition of the repeating pattern "Butterfly" until the positions are exhausted in order to synthesize all the contributions of the items of 1 ^st species, represented by Rt.

For non-linear items grouped into a single RM term

PIREsol = - Rt + Butterfly ((C / No) req, R _NL , -1) [E8]

Figure 4 shows the use of the butterfly operator to determine the link ^budget in the case where there are only 1 ^ΘrΘ species positions. The method, knowing the value (C / N _o ) req determines the value of PIREsol using the relation [E4] and the following formula obtained using the relation [E7]:

QaF = R1 // R2 // // Rn [E9]

Figures 5 and 6 show the use of the operator to determine the link budget in the case where, in the system, coexist stations of the first kind and positions of the second kind. The method can determine EIRPsool in two equivalent ways:

• using the relationship [E4] and the two following relationships (see Figure 5): Rt = RI // R2 // // Rp [E10] obtained using [E7]

QaF = Rt (1 - p / R _NL ) [E11] in linear scale

• or using the relations [E10] and [E8] explained later in the description (see Figure 6).

Figures 4, 5 and 6 show an example of concatenation of the elementary operator "Butterfly". The result of this concatenation is referred to in Figure 5 "Fast Butterfly Transform" or TPR. This transform applies only to items of 1 ^ΘrΘ species.

FIG. 6 represents an example of calculation of EIRPOL for a set comprising 7 disturbing stations, with 5 stations of 1 ^ΘrΘ species and 2 stations of the second kind. The value of PIREsol is obtained by applying the relation [E8].

Variations of implementation described above, it follows that:

• The greater the QaF, the lower the EIRP needed at the wanted rate D (or equivalently, the higher the D rate at

Perry fixed),

• We obtain a null QaF (ie the same figure of EIRP as of C / No required) for a jammer of 0 dBW / Hz emission density (example: 76 dBW spread in a 40 MHz bandwidth repeater), • We obtain a Negative QaF (ie EIRP figure> C / No digit required) for a stronger scrambler spread in the same repeater band. According to an alternative embodiment, the quality indicator is used to size the links and in particular the reception antennas.

For this, the method unfolds for example the steps described below: The QaF quality indicator is expressed as a function of the reception antenna surface of a station. This leads to a curve that can be likened to a high-pass Butterworth filter defined by a slope, a gain and a cutoff antenna at -3 dB.

The individual quality factor of the downward thermal station R ₂ is expressed in the following logarithmic form:

R ₂ = Ri + 20 log10 (- ^ -) [E12]

0-3 with:

Ri the individual quality factor of the term thermal term amount = gain of the filter in the bandwidth. 0 the diameter of the receiving station antenna

0-3 the parameter called cutoff antenna diameter at -3 dB.

We deduce the "frequency" response of the aforementioned R-ι // R ₂ filter in linear scale:

QaF = R ₁ ( ⁰ ) [E13]

0 ² + 0f ₃

The calculation and the rate of the filter are generalizable to N terms of disturbance of the link budget. The log-log scale of FIG. 7 makes it possible to identify 2 zones:

• An area where the antenna diameter is greater than the cutoff antenna diameter at -3 dB: the rising thermal noise is dominant and it imposes the balance sheet, • An area where the antenna diameter is less than the cutoff antenna diameter at -3 dB: the descending thermal noise is dominant.

If the receive ground antenna diameter is equal to the cut-off antenna diameter at -3 dB then the linear relationship QaF = 0.5 R1 and there is equilibrium between the rising thermal noise disturbance and the noise disturbance descending thermal.

Each curve of variation of QaF (as a function of the square of the diameter of the receiving antenna) can be parameterized by: - the coverage of the satellite channel and / or the operational gain of the repeater,

- the level of friend and / or enemy interference,

- the elevation angle of the stations and / or the total noise temperature,

- etc.

These curves are configurable and presented at the request of the operator so that the latter chooses in the value range determined by the calculation tool according to the invention, the relevant combinations of sizing parameter values that meet the operational requirement ( eg flow, BER and scrambler level) and the degrees of freedom of the future network to be deployed (eg coverage and ground antenna array).

The following example of practical application is given as an illustration and in no way to limit the understanding of the various steps of the process according to the invention.

Table 1 summarizes quantities on the link budgets in the field of space telecommunications.

All the following quantities are either calculated by the tool or entered by the user, with the exception of the Boltzman constant. Disturbance of thermal noise amount:

P ₁ = (0 / No) ₁ = Worst _0I - A _up + (G / T) _satB + AvGeo _up - 10logK [E14]

We thus have the linear and homogeneous relation:

Characteristics of the transparent repeater: The characteristics given in the specifications of the transparent repeater are usually the following ones:

Table 2

In the linear or quasi-linear zone of the repeater, the operational gain Gop (here including the antenna patterns) is provided by the following logarithmic scale relation:

(PIRE _its turationBZ- OBO) = (Cj _n _satu ration BZ ^~ 'BO) + G _op BZ with:

Cin saturationBZ = DFS ₆ Z - 1 Olθg (4π / λ _up ² )

DFSBZ = DFSezmin + ATNsat

we also have the relation in logarithmic scale: PIRE _its t = C] _n + G _op with:

Cj _n = WORSE _S0 | - A _up

Gop = GopBZ + AvGeo _U p + AvGeOdown

hence the following two relations in logarithmic scale:

Worse _S at = Worst ₀ I - A _up + AvGeo _up + AvGeo _dO wn + G _opB z [E16]

G _O pBz = PIREsaturatio _n BZ-OBO + IBO-DFS _B zmi _n -ATN _sat + 10log (4π / λ _up ² ) [E17]

Perturbation of descending thermal noise:

P ₂ = (C / No) ₂ = WORSE _S atBZ - A _dO wn + (G / T) _S0 | + AvGeo _dO wn - 10logK [E18] with:

WORST WORST _his t = _S + atBZ AvGeo _of own Combining [E16] and [E18] gives:

P2 = EARN _SO | -Aup-A _of own + AvGeθup + AvGeθ _of own + GopBZ + (G / T) _sor 1 OlogK [E19] Moreover, (G / T) _SO ι can be calculated by separating the two terms:

• T = temperature of the system T _sys in reception (see the state of the art)

• G = receive antenna gain. If the (G / T) _SO ι is calculated at the input of the low noise amplifier LNA of the station, then it is necessary to withdraw from the reception antenna gain the line losses noted L | i _gne between the foot of antenna and the LNA.

Next, the attenuation of free space A _e is grouped together _. ι _. on the downward path with the receive ground antenna gain G to remove the wavelength of the carrier on the descent.

We recall the formula of the attenuation of free space (in linear scale):

Ae.i. = (-p-) ² [E20]

4π d

For a parabolic antenna of diameter 0 and efficiency η, the reception gain in the axis is (in linear scale):

G = η ± f ≈ n φ * [E21] λ ^{2 λ}

We deduce: A _e ι G = η (-) ² [E22]

4 d

This relationship is independent of the frequency.

By combining the relations [E19] and [E22], we find in logarithmic scale the following relation: P ₂ = PIREsoi - A _up - M _down + AvGeo _up + AvGeo _down + G _opB z -1 OlogT _sys -

10logK +1 Ologη -20log d -12dB + 20log 0 - L | _ig ne with: d = distance between the satellite and the receiving station.

The "receive antenna at -3 dB" is the reception antenna diameter denoted 0-3 which corresponds to the equilibrium Ri = R ₂ . By putting the following equation in logarithmic form: 2Olog0 _-3 = (G / T) _sat BZ + M _down - AvGeo _dO wn -G BZ _OP + 10logT _sys -1 Ologη + 20log d +12 dB + L | _ig ne [E23]

we find: R ₂ = Ri + 2Olog0 -2Olog0 _-3 [E12] (already mentioned) and we have the homogeneous equivalent relation in linear form:

( _0.3 ) ² _{? =} f MG-Lλ 16 d ² T _s ^ _v ! _s - M ^(α i _o ^o _w ^w _n ⁿ Li ^l; gg ⁱ _n n _e e _[[≡24] v ^G ^T ΛatBZ opBZ η ^AvGeo down

Ri // R ₂ is simplified from the 0/0 _-3 radio and the Butterfly operator, by factorizing Ri.

By plotting log-log the curve Ri // R ₂ versus 2Olog0, we obtain a high-pass filter in the domain of the antenna surfaces with a breaking antenna 0 _-3 , a gain corresponding to the asymptotic value Ri, and an attenuated asymptotic zone R ₂ = a + b0 ² , a slope of 10 dB per decade or 3 dB per octave if the abscissa is graduated to 2Olog (0).

More generally, the method according to the invention can be used in any link sizing. The sizing consists in particular in finding the right tradeoffs between the following quantities: a) the operational gains of the repeater (related to the coverage thus to the edge antennas, and to an attenuator edge setting), b) the antenna size of the park of ground segment stations, c) EIR ground per link (in relation to the antenna size that gives the station EIRP and the number of links), d) the user rate per link (in connection with the performance of Eb / No. of the ground modem), e) the level of interference from interference (compliance with ITU coordination agreements or intergovernmental agreements) or enemy interference (interference).

To help an operator of the network management and planning center to find a good dimensioning, the method according to the invention has the particular advantage of presenting to the operator: i) an independent indicator points c) and d); it is the QaF which establishes the exchange relation PIREsol, D, Eb / No and Margin, ii) The sensitivity of this indicator to the points a) b) and e): it is the family of curves of variation of QaF which is doubly parameterized by the coverage (payload operational gain) and the threat / interference level.

Without departing from the scope of the invention, the method is also applicable in a system using an aircraft as a communication node, either in transparent mode (on-board repeater) or in non-transparent mode (on-board processing). The aircraft is for example a drone or a plane, helicopter or any other device having the same functions. The [E1] to [E4] relationships previously introduced are used except for the relation [E4] in which the extreme term on the right takes into account the separation of the uplink and downlink budget if the repeater is non-transparent. Other terms of interference will be added.

Claims

1 - Method for planning and / or dimensioning links between several stations or stations in a wireless telecommunications system comprising at least the following steps: a) establishing, by existing link and on a logarithmic scale, a relationship between the effective radiated power , PIREsol, the required signal-to-noise density ratio (C / No) req for a link, and a quality indicator QaF, b) determining the quality indicator QaF from the contribution of the first-order disturbance stations which are linear in PIREsol and substages of the second kind that are non-linear in PIREsol.

2 - Process according to claim 1 characterized in that it comprises a step c) of determining the PIREsol from the quality indicator

QaF determined in step b).

3 - Process according to claim 1 characterized in that for determining the quality indicator QaF in the case of items of the first kind, the items of the first type 2 by 2 are grouped together and the Butterfly operator (R ₁ , R) is applied. ₂ , sign) = min (R ₁ , R ₂ ) -10 log ₁₀ (1 + sign .i _O ^{("1 (R1" R2} > ^{/ 1} ° 1>), with sign = + 1, and this operator is repeated until that there are no more posts of the first kind.

4 - Process according to claim 2 characterized in that to determine the PIREsol for a network comprising positions of the first kind and positions of the second kind, using the relationship established in step a) and the following two relations: Rt = IR II P2. II // Rp [EI O] obtained using Butterfly (R ₁ , R ₂ , sign) = min (R ₁ , R ₂ ) -10 log ₁₀ (1 + sign .io ^{("1 (R 1" R 2) / 10 | )} ), with sign = + 1 QaF = Rt (1 - p / RNL) with

5 - Process according to claim 2 characterized in that to obtain the PIREsol is used: PIREsol = - Rt + Butterfly ((C / No) req, R _NL , -1)

Where Butterfly (R ₁ , R ₂ , sign) = min (R ₁ , R ₂ ) -10 log ₁₀ (1 + sign .10 ^{("1 (R 1" R 2) / 10 |)} ), and

6 - Process according to claim 1 characterized in that the system comprises a satellite (ie transparent repeater), the stations comprising a Satcom antenna (transmission and reception), the quality indicator is expressed as a function of the antenna surface of receiving a station and defining the area where the rising thermal noise is dominant and an area where the descending thermal noise is dominant, an area being associated with an antenna diameter.

7 - Method according to one of claims 1 to 5 characterized in that the telecommunications system is a regenerative satellite (ie with on-board processing) and that the uplink and the downlink are treated separately with each one or more stations of disruption in the balance sheet of its connection.

8 - Method according to one of claims 1 to 5 characterized in that the telecommunications system is composed of a terrestrial segment with stations communicating with each other and an air segment which serves as a communication relay. 9 - Device for dimensioning and / or planning the links between several stations in a wireless telecommunications system comprising, the central station and the remote stations being equipped with a processor adapted to perform the steps of one of claims 1 to 7.